Process for polymerization of α-olefins

ABSTRACT

Stereospecific polymerization of α-olefins is carried out with use of a catalyst comprising an activated titanium component obtained by treating products of copulverization of magnesium halides and aromatic orthocarboxylic acid esters with titanium halides, an organoaluminum compound and an electron donative compound. α-Olefin polymers of high stereospecificity are thus obtained with a high polymerization activity.

BACKGROUND OF THE INVENTION

This invention relates to a process for the stereospecificpolymerization of α-olefins and a catalyst therefor.

It is well-known and has now been conducted in a commercial scale thatα-olefins such as propylene and butene are polymerized in the presenceof a so-called Ziegler-Natta catalyst comprising titanium trichlorideand an organoaluminum compound to form a stereospecific poly-α-olefin.

Recently, methods supported the titanium component of Ziegler-Nattacatalysts on a carrier for improving the catalyst activity have beendeveloped and generally, have being employed for a catalyst forpolymerization of ethylene. In case of polymerization of α-olefins suchas propylene and butene, a useful, crystalline polymer cannot beobtained unless the polymeric chain has an isotactic structure in whichalkyl groups such as methyl or ethyl are stereospecifically regulated.Therefore, catalysts improved only in polymerization activity as thecase of polymerization of ethylene cannot be considered to be a usefulcatalyst for polymerization of α-olefins and thus, regulating astereospecificity of polymer is significant matters.

In connection with this, there were provided methods including the stepof adding an electron donative compound as the third component to acombination of a carrier type titanium component having a titaniumcompound supported on magnesium halides and an organoaluminum compoundthereby improving the stereospecificity of polymer. For example, BritishPat. No. 1,387,890 discloses catalysts comprising a titanium halidecomposition, an organoaluminum compound and an electron donativecompound, said titanium halide composition being prepared by pulverizingmagnesium halides together with titanium halides or pulverizing acomplex of titanium halides and an electron donative compound togetherwith magnesium halides. These catalysts are, however, still insufficientin a polymerization activity and a crystallinity of polymers obtained.

SUMMARY OF THE INVENTION

An object of this invention is to provide a process for thestereospecific polymerization of α-olefins, obtaining polymers of highstereospecificity with a high polymerization activity.

Another object of this invention is to provide a carrier type of thetitanium catalyst component, providing a poly-α-olefin with an improvedpolymerization activity and stereospecificity.

The foregoing and other objects will fundamentally be attained bypolymerizing α-olefins in the presence of a catalyst comprising acarrier type titanium component obtained by contact treatment ofcopulverized products of magnesium halide and an aromaticorthocarboxylic acid ester with titanium halide, an organoaluminumcompound and an electron donative compound.

According to another embodiment of this invention, the stereospecificpolymerization of α-olefins may be carried out in the presence of acatalyst comprising a carrier type titanium component obtained bycontact treatment of copulverized products of magnesium halide, aluminumhalide and an aromatic orthocarboxylic acid ester with titanium halide,an organoaluminum compound and an electron donative compound.

According to still another embodiment of this invention, a titaniumcomponent obtained by contact treatment of copulverized products ofmagnesium halide, an aluminum halide-organic acid ester complex and anaromatic orthocarboxylic acid ester with titanium halide may be used forthe carrier type titanium component for a polymerization catalyst ofα-olefins.

According to further another embodiment of this invention, a titaniumcomponent obtained by contact treatment of copulverized products ofmagnesium halide, aluminum halide, an aromatic orthocarboxylic acidester and an organosilicon compound having at least one alkoxyl groupwith titanium halide may be used for the carrier type titanium componentfor a polymerization catalyst of α-olefins.

DETAILED DESCRIPTION OF THE INVENTION

Magnesium halides which may be used in the preparation of the carriertype titanium component are, preferably, a substantially anhydrousmagnesium halide and particularly, magnesium chloride is preferred.

An aromatic orthocarboxylic acid ester which may be used is representedby the formula, ##STR1## where R¹ is an aromatic hydrocarbon radical andeach of R², R³ and R⁴ which may be the same or different is ahydrocarbon radical. Preferably, derivatives of orthobenzoic acid estersor orthonaphthoic acid esters are used. As for R², R³ and R⁴, analiphatic hydrocarbon radical of 1-10 carbon atoms is preferred.Examples of these compounds include methyl orthobenzoate, ethylorthobenzoate, methyl orthotoluylate, ethyl orthotolaylate, ethylorthoanisate and propyl orthoanisate.

This invention is characterized by using aromatic orthocarboxylic acidesters, and with use of an aliphatic orthocarboxylic acid ester thedesired effects cannot be attained as shown in the hereinafter mentionedReference Examples 3 and 6. An amount of the aromatic orthocarboxylicacid ester is not particularly limited, though 0.05-0.3 moles per 1.0mole of magnesium halide are preferred.

Aluminum halides which may be used in the preparation of the activatedtitanium catalyst component are, preferably, a substantially anhydrousaluminum halide and particularly, aluminum chloride is preferred. Anamount of the aluminum halide is not particularly limited, though0.5-2.0 moles per 1.0 mole of an aromatic orthocarboxylic acid ester arepreferred.

Also, an aluminum halide-organic acid ester complex which may be used inthe preparation of the activated titanium catalyst component is obtainedin the conventional methods, for example, by mixing aluminum halideswith organic acid esters at normal temperature or at elevatedtemperatures.

The organic acid ester which may be used is an aromatic carboxylic acidester, an aliphatic carboxylic acid ester and an alicyclic carboxylicacid ester. An aromatic carboxylic acid ester is preferred. Examplesinclude methyl benzoate, ethyl benzoate, methyl toluylate and the like.

An amount of the complex is not particularly limited, though 0.05-0.3moles per 1.0 mole of magnesium halide are preferred.

Furthermore, an organosilicon compound having at least one alkoxyl groupwhich may be used in the preparation of the activated titanium componentmay be represented by the formula,

    Si(OR.sup.5).sub.m X.sub.n Y.sub.p

wherein R⁵ is an alkyl group, each of X and Y is a hydrocarbon radical,halogen or a carbonyloxy group ##STR2## wherein R is an alkyl group, mis an integer of 1-4, each of n and p is 0-3 and the total of m, n and pis 4. Examples of these compounds include Si(OC₂ H₅)₃ Cl, Si(OC₂ H₅)₂Cl₂, Si(OCOCH₃)(OC₂ H₅)Cl₂, Si(OC₂ H₅)₄, Si(C₂ H₅)₂ (OC₂ H₅)₂, Si(C₆H₅)(OC₂ H₅)₃ and the like. There are particularly preferred those havingat least two alkoxyl groups, such as Si(C₂ H₅)(OC₂ H₅)₃, Si(OC₂ H₅)₄,Si(C₂ H₅)₂ (OC₂ H₅)₂ or Si(C₆ H₅)(OC₂ H₅)₃.

An amount of the organosilicon compound is not particularly limited,though 0.05-0.15 moles per 1.0 mole of magnesium halide are preferred.

For the preparation of the activated titanium catalyst component, thereis, first, formed a copulverized product of (1) a combination ofmagnesium halides and an aromatic orthocarboxylic acid ester: (2) acombination of magnesium halides, aluminum halides and an aromaticorthocarboxylic acid ester: (3) a combination of magnesium halides, analuminum halide-organic acid ester complex and an aromaticorthocarboxylic acid ester: or (4) a combination of magnesium halides,aluminum halides, an aromatic orthocarboxylic acid ester and anorganosilicon compound having at least one alkoxyl group.

In this case, a complex of aluminum halides with an aromaticorthocarboxylic acid ester which has been previously synthesized or areaction product of magnesium halides with an aromatic orthocarboxylicacid ester which has been previously synthesized may be used instead ofadding each components separately.

The pulverization process may be conducted under vacuum or atmosphere ofan inert gas and should be effected in substantially the absence ofoxygen and moisture. The pulverization conditions are not particularlylimited, though the temperature is comprised between 0° and 80° C. ingeneral. The pulverization time varies depending on types ofpulverizers, but is normally comprised between 2 and 100 hours. Next,the copulverized products thus obtained are subject to contact treatmentwith titanium halides. Examples of titanium halides which may be usedinclude titanium tetrachloride, titanium tetrabromide and the like.Particularly, titanium tetrachloride is preferred.

The contact treatment may be conveniently, effected by suspending theabove copulverized products in the titanium halide or in its solution inan inert solvent, maintaining contact at temperatures of 0°-135° C. andthen separating solid materials, followed by drying or removing freetitanium halides by washing with an inert solvent to obtain theactivated titanium catalyst component. The term of inert solvents usedherein means aliphatic, alicyclic or aromatic hydrocarbons and mixturesthereof.

In accordance with this invention, the activated titanium componentobtained above is combined with an organoaluminum compound and anelectron donative compound to form a catalyst of high activity forpolymerization of α-olefins.

The organoaluminum compound which may be used is represented by theformula,

    AlR.sub.m X'.sub.3-m

wherein R is a hydrocarbon radical, X' is an alkoxyl group, hydrogen orhalogen atoms, and m is 1.5 to 3.0. The typical examples includetriethylaluminum, tri-n-butylaluminum, tri-iso-butylaluminum,tri-n-hexylaluminum, diethylaluminum monochloride, diethylaluminumhydride, diethylaluminum ethoxide and others. These may be used alone orin mixture. A mole ratio of the organoaluminum compound to titaniummetal of the activated titanium component is not limited, though it iswithin preferably, the range of 1 to 500.

Electron donative compounds which may be used include phosphorus-,oxygen- or nitrogen-containing compounds. The phosphorus-containingcompound may be represented by the Formulae,

    P(Z.sup.1).sub.m (Y.sup.1 Z.sup.1).sub.3-m

or

    O═P(Z.sup.1).sub.m (Y.sup.1 Z.sup.1).sub.3-m

wherein Z¹ is hydrogen, a hydrocarbon radical, amino groups oralkylamino groups, Y¹ is oxygen or sulphur and m is 0 to 3. Theoxygen-containing compound may be represented by the formulae, ##STR3##or

    Z.sup.2 (COOZ.sup.3).sub.k

wherein Z² and Z³ each are a hydrocarbon radical or together may form aring and k is 1 to 3.

Examples of the nitrogen-containing compound are amines or derivativesthereof. Preferably, organic acid esters and the aromaticorthocarboxylic acid esters having the abovementioned Formula are usedfor the electron donative compound. Typical examples of the organic acidester are methyl formate, ethyl acetate, amyl acetate, methyl acrylate,methyl methacrylate, methyl benzoate, ethyl benzoate, methyl toluylate,methyl anisate and others.

The electron donative compound may be brought into contact with othercomponents at any time during the preparation of a catalyst. Theelectron donative compound may be also added when polymerization ofα-olefins is effected. Generally, there are methods of contacting theelectron donative compound after contact of the activated Ti componentwith the organoaluminum compound, contacting the activated Ti componentafter contact of the organoaluminum compound with the electron donativecompound, contacting the organoaluminum compound after contact of theactivated Ti component with the electron donative compound or contactingthe three components at the same time. It is, particularly, preferredthat a part or all of the electron donative compound to be added isallowed to exist when contacting the activated titanium component withthe organoaluminum compound to polymerize polymerizable monomers. Anamount of the electron donative compound is within, preferably, therange of 0.1 to 0.5 moles per 1.0 mole of the organoaluminum compound.When the amount exceeds 0.5 moles, it would result in a sudden decreasein polymerization activity without an further increase instereospecificity.

This invention may be applied to a homopolymerization orcopolymerization of α-olefins having the formula,

    R.sub.1 --CH═CH.sub.2

wherein R₁ is an alkyl group of 1-10 carbon atoms, or a copolymerizationof the above α-olefin with ethylene. Examples of the α-olefin arepropylene, butene-1, hexen-1, 4-methyl-pentene-1 and the like.

The polymerization procedure according to this invention may be carriedout in the conventional method using usual conditions. Thepolymerization temperature is generally in the range of 0°-100° C.,preferably 20°-90° C. and the pressure is in the range of from normalpressure to 50 atm., preferably from normal pressure to 40 atm.

In the polymerization reaction, a solvent such as an aliphatic,alicyclic or aromatic hydrocarbon or mixture thereof may be used and maybe, for example, propane, butane, pentane, hexane, heptane, cyclohexane,benzene, toluene or mixtures thereof.

Also, a bulk polymerization may be employed using liquid monomersthemselves as the solvent. Alternatively, the polymerization reactionmay be conducted in the vapour phase wherein gaseous monomers aredirectly contacted with the catalyst without use of a solvent.

The molecular weight of polymers produced by the method of thisinvention varies depending on the manner of reaction, kind of catalystand polymerization conditions. However, the molecular weight may becontrolled by adding to the reaction system, for example, hydrogen, analkyl halide and a dialkyl zinc, if necessary.

This invention will be illustrated by way of the following examples.Also, for the purpose of comparison there are set forth ReferenceExamples which are beyond the scope of this invention.

EXAMPLE 1

(A) 20.0 g of magnesium chloride and 6 ml of methyl orthobenzoate werecharged under nitrogen atmosphere into a vibration mill provided with apot of 600 ml in inner volume, in which 80 steel balls with a diameterof 12 mm were placed, and subject to pulverization for 20 hours.

10 g of the pulverized products thus obtained and 200 ml of titaniumtetrachloride were charged into a 300 ml round-bottomed flask andstirred at 80° C. for two hours and thereafter, the supernatant liquidwas removed by decantation. Next, after repeating seven times a washingtreatment consisting of the steps of stirring with 200 ml of n-heptaneat room temperature for 30 minutes and then removing the supernatantliquid by decantation, further 200 ml of n-heptane were added to obtainan activated titanium component slurry. A part of the activated titaniumcomponent slurry was sampled and subjected to analysis after evaporatingn-heptane. A titanium content of the activated titanium component was1.50% by weight.

(B) 1.0 l of n-heptane, 0.1 g of the above activated titanium component,0.375 ml of triisobutylaluminum, 0.18 ml of diethylaluminum chloride and0.08 ml of methyl orthobenzoate were charged into a stainless steelautoclave of 3.0 l in capacity under nitrogen atmosphere. Afterexhausting the nitrogen gas from the autoclave by means of a vacuumpump, gaseous hydrogen was fed till a partial pressure of 0.1 kg/cm² andthen, propylene was fed till a vapour pressure of 2 kg/cm².Gauge. Theautoclave was heated and after 5 minutes, the inner temperature waselevated to 70° C.

While feeding propylene to maintain the pressure at 5 kg/cm².Gauge,polymerization was continued at 70° C. for one hour.

After cooling the autoclave, unreacted propylene was purged and thecontents were removed, filtered and dried at 60° C. under reducedpressure.

Thus 85.4 g of a white powdery polypropylene were obtained.

Limiting viscosity number (135° C., tetralin): 1.98

Bulk density: 0.33 g/ml

Extraction residue of polymer with boiling n-heptane (hereinafterreferred to as "Powder II"):92.7%

On the other hand, 4.8 g of polymers soluble in n-heptane were obtained.The ratio of the extraction residue of polymer with boiling n-heptane tothe total polymer (hereinafter referred to as "Total II") was 87.8%. Apolymerization activity of the catalyst in this Example was 60kg/g.Ti.hr (Formation rate of polymer per gram of activated Ti perhour).

REFERENCE EXAMPLES 1 AND 2

Using 26.4 g of magnesium chloride and 3.6 g of titanium tetrachloride,a titanium component was prepared by conducting copulverization in thesame manner as in Example I (A).

Polymerization was repeated in the same manner as in Example 1 (B)except using 0.2 g of the titanium component obtained above, 0.1 ml oftriethylaluminum and ethyl benzoate as the third component. The resultsare set forth in Table 1.

REFERENCE EXAMPLE 3

In accordance with the procedure of Example 1 (A), a titanium componenthaving a titanium content of 2.5 weight % was obtained by copulverizing20 g of magnesium chloride and 6 ml of ethyl orthoacetate and theneffecting reaction with titanium tetrachloride followed by washing withn-heptane.

Using 0.1 g of the above titanium component, 0.375 ml oftriisobutylaluminum, 0.18 ml of diethylaluminum chloride and 0.08 ml ofmethyl orthobenzoate, polymerization was carried out in the sameprocedure as in Example 1 (B) for two hours.

However, polypropylene was not obtained at all.

REFERENCE EXAMPLE 4

A titanium component of 3.0 weight % in titanium content was prepared bycopulverizing 23.6 g of magnesium chloride and 6.4 g of a titaniumtetrachloride-ethyl benzoate complex in accordance with the procedure ofExample 1 (A).

Using 0.20 g of the above titanium component and 0.1 ml oftriethylaluminum, polymerization was carried out in the same procedureas in Example 1 (B).

After two hours polymerization, 110 g of a powdery polypropylene wereobtained.

Powder II: 70.3%

Limiting viscosity number: 1.80

Bulk density: 0.22 g/ml

On the other hand, 30.5 g of non-crystalline polypropylene were obtainedfrom the filtrate.

Total II: 55.0%

Polymerization activity: 11.7 kg/g.Ti.hr

Yield of polymer: 23.4 kg/g.Ti

REFERENCE EXAMPLE 5

In accordance with the procedure of Example 1 (A), a titanium componentof 1.21 weight % in titanium content was obtained by copulverizing 24.7g of magnesium chloride and 5.3 g of ethyl benzoate and then conductingreaction with titanium tetrachloride followed by washing with n-heptane.

Using 0.20 g of the above titanium component and 0.07 ml oftriethylaluminum, polymerization was carried out in the same manner asin Example 1 (B) for two hours. 218 g of a powdery polypropylene and 25g of polypropylene soluble in n-heptane were obtained.

Powder II: 95.0%

Bulk density: 0.28 g/ml

Limiting viscosity number: 1.98

Polymerization activity: 51 kg/g.Ti.hr

Total II: 85.2%

                                      Table 1                                     __________________________________________________________________________               Polymeri-                                                                           Powdery Non-crystalline                                      Reference                                                                           Ethyl                                                                              zation                                                                              Polypropylene                                                                         Polypropylene              Limiting                                                                            Bulk                Example                                                                             Benzoate                                                                           Time  Yield   Yield    Activity                                                                             Yield Total II                                                                           Viscosity                                                                           Density             No.   g    hr.   g       g        kg/g.Ti.hr.                                                                          kg/g.Ti                                                                             %    Number                                                                              g/ml                __________________________________________________________________________    1     0.02 2     62      5        5.6    11.2  83.2 1.55  0.20                2     0.05 2     30      3        2.8     5.5  82.8 1.71  0.22                __________________________________________________________________________

EXAMPLE 2

Using the catalyst component obtained in Example 1 (A), polymerizationwas carried out in the same procedure as in Example 1 (B) except usingethyl benzoate instead of methyl orthobenzoate as the third component tobe added at the time of polymerization.

The results are set forth in Table 2.

EXAMPLES 3 TO 6

An activated titanium component was prepared using various aromaticorthocarboxylic acid esters instead of methyl orthobenzoate which hadbeen used for the preparation of the activated titanium component inExample 1 (A).

Using the activated titanium component thus obtained, polymerization ofpropylene was carried out in the same manner as in Example 1 (B).

The results are set forth in Table 2.

EXAMPLE 7

Using 0.1 g of the activated titanium component obtained in Example 1(A), 0.1 ml of ethyl benzoate and 0.3 ml of diethylaluminum ethoxide,polymerization was carried out in the same manner as in Example 1 (B).

The results are set forth in Table 2.

    Table 2      Activated Ti    Component  Polymeri- Exam- *1 Ti Organoaluminum     Compounds 3rd Component zation  Activity Total Limiting Bulk ple Ortho-     Content  Amount  Amount  Amount Time Yield kg/g. II Viscosity Density     No. esters wt. % Type ml Type ml Type ml hr. g Ti . hr % Number g/ml        Methyl  Triiso-  Diethyl-  Ethyl-        2 ortho- 1.50 butyl- 0.375     aluminum 0.24 benzoate 0.14 1.0 95 63 89.7 1.73 0.31  benzoate  aluminum      chloride  Ethyl  Triiso  Diethyl-  Methyl 3 ortho- 1.34 butyl- "     aluminum 0.18 ortho- 0.08 1.0 83 62 88.7 1.68 0.33  benzoate  aluminum     chloride  benzoate  Methyl  Triiso-  Diethyl-  Ethyl 4 orthotol- 1.33     butyl- " aluminum 0.24 benzoate 0.14 1.0 78 59 89.1 1.87 0.29  uylate     aluminum  chloride  Ethyl  Diethyl-  Diethyl-  Ethyl 5 orthotol- 1.27     aluminum 0.5 aluminum " benzoate " 1.0 70 55 89.3 1.75 0.28  uylate     hydride  chloride  Ethyl  Triiso-    Ethyl 6 ortho- 1.56 butyl- 0.8 --     -- benzoate " 1.0 94 60 88.2 2.0  0.31  anisate  aluminum  Methyl     Diethyl-    Ethyl 7 ortho- 1.50 aluminum 0.30 -- -- benzoate 0.1 1.0 98     65 89.2 1.98 0.28  benzoate  ethoxide     *1 Aromatic orthocarboxylic acid esters added for the preparation of an     activated Ti component.

EXAMPLE 8

(A) A copulverized product was obtained in the same manner as in Example1 (A) except using 20 g of magnesium chloride, 4.8 g of aluminumchloride and 6 ml of methyl orthobenzoate for copulverization.

10 g of the above pulverized products and 100 ml of titaniumtetrachloride were charged into a 200 ml round-bottomed flask andstirred at 80° C. for two hours and then, the supernatant liquid wasremoved by decantation. Next, after repeating seven times a washingtreatment of stirring with 100 ml of n-heptane at 80° C. for 15 minutesand then removing the supernatant liquid by decantation, further 100 mlof n-heptane were added to form an activated titanium component slurry.

A part of the activated titanium component slurry was sampled andsubjected to analysis after evaporating n-heptane. A titanium content ofthe activated titanium component was 2.20 weight %.

(B) Using 50 mg of the above activated titanium component, 0.375 ml oftriisobutylaluminum, 0.18 ml of diethylaluminum chloride and 0.08 ml ofmethyl orthobenzoate, polymerization was carried out in accordance withthe procedure of Example 1 (B).

The results are set forth in Table 3.

EXAMPLE 9

An activated titanium component was prepared in the same manner as inExample 8 (A) except using 13.2 g of a methyl orthobenzoate-aluminumchloride complex (1:1) which had been previously synthesized instead ofmethyl orthobenzoate and aluminum chloride for pulverization. A titaniumcontent of the catalyst component thus obtained was 1.97 weight %.

Polymerization was carried out in the same manner as in Example 1 (B)except using 48 mg of the above catalyst component.

The results are set forth in Table 3.

EXAMPLE 10

An activated titanium component was prepared in the same manner as inExample 8 (A) except using ethyl orthobenzoate instead of methylorthobenzoate.

Using 62 mg of the above titanium component, polymerization was carriedout in the same manner as in Example 1 (B).

The results are set forth in Table 3.

EXAMPLE 11

An activated titanium component was prepared in the same manner as inExample 8 (A) except using 4.8 g of anhydrous aluminum bromide insteadof 4.8 g of aluminum chloride for copulverization.

A titanium content of the activated titanium component thus obtained was2.21 weight %.

Polymerization was carried out in the same manner as in Example 1 (B)except using 50 mg of the above activated titanium component.

The results are set forth in Table 3.

REFERENCE EXAMPLE 6

A catalyst component was synthesized in the same manner as in Example 8(A) except using 6 ml of methyl orthoacetate instead of methylorthobenzoate for copulverization.

Polymerization was carried out in the same manner as in Example 1 (B)except using 52 mg of the above catalyst component. Polymers were,however, not obtained at all.

                                      Table 3                                     __________________________________________________________________________    Activated    Organoaluminum                                                   Ti Component Compounds                                                                      Tri-  Diethyl-                                                                            Electron                                                                            Polymeri-                                     Ex-      Ti   isobutyl-                                                                           aluminum                                                                            Donative                                                                            zation           Total                                                                             Limiting                                                                           Bulk                ample                                                                             Ortho-                                                                             Content                                                                            aluminum                                                                            chloride                                                                            Compounds                                                                           Time  Yield                                                                             Activity                                                                             II  Viscosity                                                                          Density             No. esters                                                                             wt.% ml    ml    (ml)  hr.   g   kg/g.Ti.hr                                                                           %   Number                                                                             g/ml                __________________________________________________________________________        Methyl                Methyl                                              8   ortho-                                                                             2.20 0.375 0.18  orthoben-                                                                           1.0   238 225    89.9                                                                              1.90 0.32                    benzoate              zoate                                                                         (0.08)                                                  Methyl                Methyl                                              9   ortho-                                                                             1.97 "     "     orthoben-                                                                           1.0   240 253    90.8                                                                              1.55 0.28                    benzoate              zoate                                                                         (0.08)                                                  Ethyl                 Methyl                                              10  ortho-                                                                             1.61 "     "     orthoben-                                                                           1.0   245 278    88.6                                                                              1.53 0.31                    benzoate              zoate                                                                         (0.08)                                                  Methyl                Methyl                                              11  ortho-                                                                             2.21 "     "     orthoben-                                                                           1.0   195 184    88.9                                                                              1.93 0.32                    benzoate              zoate                                                                         (0.08)                                              __________________________________________________________________________

EXAMPLE 12

(A) Using 20 g of magnesium chloride, 3.8 g of an aluminumchloride-ethyl benzoate complex (1:1) and 4 ml of methyl orthobenzoatefor copulverization, copulverized products were prepared in the samemanner as in Example 1 (A).

An activated titanium component was prepared in the same manner as inExample 8 (A) except using 10 g of the above copulverized product. Thetitanium content was 2.10 weight %.

(B) Using 62 mg of the above activated titanium component, 0.375 ml oftriisobutylaluminum, 0.24 ml of diethylaluminum chloride and 0.14 ml ofethyl benzoate, polymerization was carried out in the same manner as inExample 1 (B).

The results are set forth in Table 4.

EXAMPLE 13

Using 20 g of magnesium chloride, 11.9 g of an aluminum chloride-ethylbenzoate complex (1:1) and 1.0 ml of methyl orthobenzoate forcopulverization, an activated titanium component was prepared in thesame manner as in Example 12. Polymerization was conducted in the samemanner as in Example 12 (B) except using 69 mg of the above activatedtitanium component.

The results are set forth in Table 4.

                                      Table 4                                     __________________________________________________________________________                           Polymeri-                                              Activated Ti Component zation           Total                                                                             Limiting                                                                           Bulk                         Example                                                                            Org. Carboxylic                                                                         Aromatic                                                                              Time  Yield                                                                             Activity                                                                             II  Viscosity                                                                          Density                      No.  acid ester complex                                                                      orthoester                                                                            hr    g   kg/g . Ti . hr                                                                       %   Number                                                                             g/ml                         __________________________________________________________________________         Ethyl benzoate/                                                                         Methyl                                                         12   aluminum chloride                                                                       orthobenzoate                                                                         1.0   199.6                                                                             156    94.6                                                                              1.41 0.24                              complex                                                                       (3.8 g)   (4 ml)                                                              Ethyl benzoate/                                                                         Methyl                                                         13   aluminum chloride                                                                       orthobenzoate                                                                         "     224.4                                                                             153    94.1                                                                              1.51 0.24                              complex                                                                       (11.9 g)  (1 ml)                                                         __________________________________________________________________________

EXAMPLE 14

(A) 20 g of magnesium chloride, 5.6 g of aluminum chloride, 4 ml ofmethyl orthobenzoate and 2 ml of tetraethoxysilane were charged into thevibration mill used in Example 1 (A) and pulverized for 40 hours. Using10 g of the above pulverized products, an activated titanium componentwas prepared in the same manner as in Example 8 (A). The titaniumcontent was 2.23 weight %.

(B) Using 65 mg of the above titanium component, 0.375 ml oftriisobutylaluminum, 0.24 ml of diethylaluminum chloride and 0.14 ml ofethyl benzoate, polymerization was carried out in the same manner as inExample 1 (B).

The results are set forth in Table 5.

EXAMPLE 15

Using the activated titanium component obtained in Example 14 (A),polymerization was carried out in the same manner as in Example 14 (B)except using 0.08 ml of methyl orthobenzoate and 0.18 ml ofdiethylaluminum chloride instead of 0.14 ml of ethyl benzoate and 0.24ml of diethylaluminum chloride, respectively.

The results are set forth in Table 5.

EXAMPLE 16

An activated titanium component was prepared in the same manner as inExample 14 (A) except using 2 ml of ethyltriethoxysilane instead oftetraethoxysilane for pulverization.

The titanium content was 2.20 weight %.

Polymerization was carried out in the same manner as in Example 14 (B)except using 58 mg of the above activated titanium component.

The results are set forth in Table 5.

EXAMPLE 17

An activated titanium component was prepared in the same manner as inExample 14 (A) except using 4.0 ml of ethyl orthobenzoate instead ofmethyl orthobenzoate for pulverization.

Using 62 mg of the above titanium component, polymerization was carriedout in the same manner as in Example 14 (B).

The results are set forth in Table 5.

EXAMPLE 18

An activated titanium component was prepared in the same manner as inExample 14 (A) except using 2 ml of methyl orthobenzoate and 6 ml oftetraethoxysilane for pulverization. The titanium content was 3.2 weight%.

Polymerization was carried out in the same manner as in Example 14 (B)except using 61 mg of the above titanium component.

The results are set forth in Table 5.

EXAMPLE 19

Using the titanium component obtained in Example 14 (A), polymerizationwas carried out in the same manner as in Example 14 (B) except using0.25 ml of ethyl benzoate.

The results are set forth in Table 5.

                                      Table 5                                     __________________________________________________________________________                  Organoaluminum                                                  Activated Ti  Compounds                                                       Component           Diethyl-                                                                            Electron                                                                            Polymeri-                                         Ortho-                                                                             Organic                                                                            Triisobutyl-                                                                        aluminum                                                                            Donative                                                                            zation           Total                                                                             Limiting                                                                           Bulk                Ex. esters                                                                             Silanes                                                                            aluminum                                                                            chloride                                                                            Compounds                                                                           Time  Yield                                                                             Activity                                                                             II  Viscosity                                                                          Density             No. (ml) (ml) ml    ml    (ml)  hr    g   kg/g . Ti . hr                                                                       %   Number                                                                             g/ml                __________________________________________________________________________        Methyl                                                                             Tetra-           Ethyl                                               14  ortho-                                                                             ethoxy-                                                                            0.375 0.24  benzoate                                                                            1.0   160 113    94.4                                                                              1.53 0.33                    benzoate                                                                           silane                                                                   (4.0)                                                                              (2.0)            (0.14)                                                  Methyl                                                                             Tetra-           Methyl                                              15  ortho-                                                                             ethoxy-                                                                            "     0.18  ortho-                                                                              1.0   182 128    94.0                                                                              1.68 0.34                    Benzoate                                                                           silane           benzoate                                                (4.0)                                                                              (2.0)            (0.08)                                                  Methyl                                                                             Ethyl-           Ethyl                                               16  ortho-                                                                             trieth-                                                                            "     0.24  benzoate                                                                            "     220 178    94.3                                                                              1.41 0.28                    benozate                                                                           oxysilane                                                                (4.0)                                                                              (2.0)            (0.14)                                                  Ethyl                                                                              Tetra-           Ethyl                                               17  ortho-                                                                             ethoxy-                                                                            "     "     benzoate                                                                            "     201 134    93.1                                                                              1.55 0.25                    benzoate                                                                           silane                                                                   (4.0)                                                                              (2.0)            (0.14)                                                  Methyl                                                                             Tetra-           Ethyl                                               18  ortho-                                                                             ethoxy-                                                                            "     "     benzoate                                                                            "     165  85    94.2                                                                              1.48 0.35                    benzoate                                                                           silane                                                                   (2.0)                                                                              (6.0)            (0.14)                                                  Methyl                                                                             Tetra-           Ethyl                                               19  ortho-                                                                             ethoxy-                                                                            "     "     benzoate                                                                            "      95  69    93.8                                                                              1.48 0.30                    benzoate                                                                           silane                                                                   (4.0)                                                                              (1.0)            (0.25)                                              __________________________________________________________________________

REFERENCE EXAMPLE 7

An titanium component of 3.48 weight % in titanium content was preparedin the same manner as in Example 8 by copulverizing 20 g of magnesiumchloride and 6 ml of tetraethoxysilane and effecting reaction withtitanium tetrachloride followed by washing with n-heptane.

Using 58 mg of the above titanium component, 0.20 ml of ethyl benzoateand 0.5 ml of triethylaluminum, polymerization was carried out in thesame manner as in Example 8 (B) for one hour.

69 g of a powdery polypropylene and 2.1 g of polypropylene soluble inn-heptane were obtained.

Powder II: 95.8%

Bulk density: 0.30 g/ml

Limiting viscosity number: 1.89

Activity: 35 kg/g.Ti.hr

Total II: 93.0%

What is claimed is:
 1. In a process for the stereospecificpolymerization of α-olefins with use of a catalyst comprising a titaniumcompound supported on a carrier, an organoaluminum compound and anelectron donative compound, the improvement which comprises using anactivated titanium compound obtained by contact treatment of magnesiumhalide and an aromatic orthocarboxylic acid ester with titanium halideas the titanium compound supported on a carrier.
 2. The process of claim1 wherein said aromatic orthocarboxylic acid ester is represented by theformula, ##STR4## wherein R¹ is an aromatic hydrocarbon radical and eachof R², R³ and R⁴ which may be the same or different is a hydrocarbonradical.
 3. The process of claim 1 wherein said magnesium halide ismagnesium chloride.
 4. In a process for the stereospecificpolymerization of α-olefins with use of a catalyst comprising a titaniumcompound supported on a carrier, an organoaluminum compound and anelectron donative compound, the improvement which comprises using anactivated titanium compound obtained by contact treatment of magnesiumhalide, an aromatic orthocarboxylic acid ester and an aluminum halidewith a titanium halide as said titanium compound supported on a carrier.5. The process of claim 4 wherein said aromatic orthocarboxylic acidester is represented by the formula, ##STR5## wherein R¹ is an aromatichydrocarbon radical and each of R², R³ and R⁴ which may be the same ordifferent is a hydrocarbon radical.
 6. The process of claim 4 whereinsaid magnesium halide is magnesium chloride and said aluminum halide isaluminum chloride.
 7. In a process for the stereospecific polymerizationof α-olefins with use of a catalyst comprising a titanium compoundsupported on a carrier, an organoaluminum compound and an electrondonative compound, the improvement which comprises using an activatedtitanium compound obtained by contact treatment of magnesium halide, anaromatic orthocarboxylic acid ester and an aluminum halide-organic acidester complex with a titanium halide as said titanium compound supportedon a carrier.
 8. The process of claim 7 wherein said aromaticorthocarboxylic acid ester is represented by the formula, ##STR6##wherein R¹ is an aromatic hydrocarbon radical and each of R², R³ and R⁴which may be the same or different is a hydrocarbon radical.
 9. Theprocess of claim 7 wherein said magnesium halide is magnesium chlorideand said aluminum halide is aluminum chloride.
 10. The process of claim7 wherein said aluminum halide-organic acid ester complex is an aluminumhalide-aromatic carboxylic acid ester complex.
 11. In a process for thestereospecific polymerization of α-olefins with use of a catalystcomprising a titanium compound supported on a carrier, an organoaluminumcompound and an electron donative compound, the improvement whichcomprises using an activated titanium compound obtained by contacttreatment of a magnesium halide, an aromatic orthocarboxylic acid ester,an aluminum halide and an organanosilicon compound having at least onealkoxyl group with a titanium halide as said titanium compound supportedon a carrier.
 12. The process of claim 11 wherein said aromaticorthocarboxylic acid ester is represented by the formula, ##STR7##wherein R¹ is an aromatic hydrocarbon radical and each of R², R³ and R⁴which may be the same or different is a hydrocarbon radical.
 13. Theprocess of claim 11 wherein said magnesium halide is magnesium chlorideand said aluminum halide is aluminum chloride.
 14. The process of claim11 wherein said organosilicon compound is represented by the formula,

    Si(OR.sup.5).sub.m X.sub.n Y.sub.p

wherein R⁵ is an alkyl group, each of X and Y is a hydrocarbon radical,halogen or a carbonyloxy group ##STR8## wherein R is an alkyl group, mis an integer of 1 to 4, each of n and p is 0-3 and the total of m, nand p is 4.